Achilles Bursa Injection

Indications and Clinical Considerations

Bursae are formed from synovial sacs that allow easy sliding of muscles and tendons across one another at areas of repeated movement. These synovial sacs are lined with a synovial membrane that is invested with a network of blood vessels that secrete synovial fluid. Inflammation of the bursa results in an increase in the production of synovial fluid with swelling of the bursal sac. With overuse or misuse, these bursae may become inflamed, enlarged, and on rare occasions infected. Although there is significant intrapatient variability as to the number, size, and location of bursae, anatomists have identified a number of clinically relevant bursae, including the Achilles bursa. The Achilles bursa, which is sometimes incorrectly referred to as the retrocalcaneal bursa , lies beneath the Achilles tendon, which is the insertional tendon of the gastrocnemius muscle to the posterior calcaneus ( Fig. 186.1 ). The retrocalcaneal bursa is located behind the calcaneus. A bursa may also exist superficial to the Achilles tendon and is known as the superficial Achilles bursa ( Fig. 186.2 ). This bursa may exist as a single bursal sac or in some patients as a multisegmented series of sacs that may be loculated.

Patients with Achilles bursitis experience pain over the posterior heel and tenderness anterior to the Achilles tendon itself. The patient with Achilles bursitis may report increased pain on full passive plantarflexion of the foot. Activity involving repetitive plantarflexion, such as running, makes the pain worse, but rest and heat provide some relief ( Fig. 186.3 ). Often, the patient is unable to stand on tiptoes or walk up stairs. The pain is constant and is characterized as aching and may interfere with sleep. Coexistent Achilles tendinitis, arthritis, or internal derangement of the ankle may confuse the clinical picture after trauma to the knee joint. If the inflammation of the Achilles bursae becomes chronic, calcification of the bursae may occur.

Physical examination may reveal point tenderness in front of the Achilles tendon at its insertion at the calcaneus. Swelling and fluid accumulation often surround the bursa. Active resisted plantarflexion of the foot reproduces the pain. Sudden release of resistance during this maneuver markedly increases the pain. Rarely, the Achilles bursa may become infected in a manner analogous to infection of the prepatellar bursa.

Plain radiographs of the knee may reveal calcification of the bursa and associated structures, including the Achilles tendon, consistent with chronic inflammation ( Fig. 186.4 ). Magnetic resonance imaging, computed tomography, and/or ultrasound is indicated if bursitis, internal derangement, occult mass, tumor of the ankle, or Achilles tendinopathy is suspected and to help confirm the diagnosis ( Fig. 186.5 ). Electromyography helps distinguish Achilles bursitis from neuropathy, lumbar radiculopathy, and plexopathy. The injection technique described later serves as both a diagnostic and a therapeutic maneuver.

Clinically Relevant Anatomy

The Achilles bursa lies between the Achilles tendon and the base of the tibia and the posterior calcaneus (see Fig. 186.1 ). The bursa is subject to the development of inflammation after overuse, misuse, or direct trauma. The Achilles tendon is the thickest and strongest tendon in the body, yet it is also very susceptible to rupture. The common tendon of the gastrocnemius muscle, the Achilles tendon begins at midcalf and continues downward to attach to the posterior calcaneus, on which it may become inflamed (see Fig. 186.3 ). The Achilles tendon narrows during this downward course, becoming most narrow approximately 5 cm above its calcaneal insertion. It is at this narrowest point that tendinitis also may occur. Tendinitis, especially at the calcaneal insertion, may mimic Achilles bursitis and may make diagnosis difficult.